Activity had decreased by 4 October, and continued to decline the following week. Continuous tremor after 3 October and into early November had a maximum amplitude of 0.23-0.53 µm, registered 11 km from the volcano. On 5 and 7-9 October the volcano was obscured by clouds, but on 6 October the fumarolic plume from the summit crater rose ~600 m above the rim and was directed NE. Observers in Kliuchi [(30 km NNE)] reported decreased activity during 8-15 October. Gas-and-steam columns rising from two apertures at the summit reached 2,500 m above the crater on 10 October and 800 m on 14 October. Once again during clear weather a gas-and-steam column was seen rising 200 m above the summit crater on 17, 22, and 23 October and to 800-1,500 m on 18-20 October. During 27-29 October the column rose 200-800 m above the summit. The volcano was obscured by clouds from 30 October to 2 November.

Geological Summary. Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: V. Kirianov, IVGG; AVO.